THE RED-LETTERED 'RR' EMBLEM affixed to the downsized Pantheon grille on the Rolls-Royce 103EX is a reminder — if you needed one — that this car is purely experimental. Like the blown-glass illuminated Spirit of Ecstasy, the grille is purely cosmetic — there is no radiator or internal combustion engine behind it — but too dear to the marque to be excluded from the design, even as its creators contemplate the next century in the most forward-thinking ways possible.